. >> reporter: democrats are pressing hard with a rally starring former president bill clinton. and, of course, a close race means negative ads. >> congressman jeff flake helps himself, not us. >> my opponent was hand picked by president obama. so you know what he'll do. negative advertising works, unfortunately. >> reporter: barack obama's rubber stamp. >> no campaign ever wants to see their ads as negative. they're contrast pieces. >> reporter: with carmona leading by up to 10% among women, flake's campaign is airing this contrast piece. >> carmona's not who he seems. he has issues with anger, with ethics and with women. >> reporter: the carmona campaign fired back. >> rich treats everyone with respect. it doesn't matter whether you're fael or female. >> the key to this race could be arizona's latino population. carmona has a commanding lead among hispanics by more than three to one and on the campaign trail he plays up his puerto rican heritage. >> because i am one of them. they understand i understand the culture, the language, and the challenges of emigrant families. >> rep